1. Technical Field
The present invention relates to a method for setting a parameter expressing a measurement condition of three-dimensional measurement to a three-dimensional visual sensor and the three-dimensional visual sensor to which the method is adopted. In the three-dimensional visual sensor, the three-dimensional measurement is performed by image processing, predetermined recognition processing is performed based on a measurement result, and a recognition result is outputted as numerical data.
2. Related Art
For example, when three-dimensional recognition processing is performed in order to cause a robot to grasp a component in a manufacturing scene, three-dimensional information restored by three-dimensional measurement of a stereo camera is checked with a previously registered three-dimensional model of a recognition-target object to recognize a position and an attitude (specifically, a rotation angle with respect to three-dimensional model) of the recognition-target object (for example, see Japanese Unexamined Patent Publication No. 2000-94374).
In this kind of recognition processing, there has been proposed a method (segment based stereo method) in which an edge in a stereo image is divided into units called “segment”, and a stereo correspondence search is performed in units of segments to restore three-dimensional information on a contour (see “Correspondence Evaluation Based On Connectivity In Segment Based Stereo”, Journal of Information Processing, vol. 40, No. 8, pp. 3219-3229, August, 1999).
Recently the applicant develops a general-purpose three-dimensional visual sensor. In the general-purpose three-dimensional visual sensor, it is necessary that a user perform setting processing such as camera positioning, calibration, and three-dimensional model registration. Additionally, it is necessary that the user set various parameters expressing measurement conditions according to a processing purpose or a feature of a recognition-target object.
For example, in the three-dimensional measurement in which the stereo image is used, generally an edge in an image is extracted as a measurement target. In such cases, it is necessary to set a threshold of density gradient strength such that the edge of the target is accurately extracted. Occasionally various measurement conditions concerning supplementation of a feature point and noise reduction are set in order to enhance recognition accuracy even after a three-dimensional coordinate is computed by correlating the stereo images to each other.
Accordingly, in order to perform stable recognition, it is necessary to set various parameters expressing the measurement conditions to proper values. However, in order to find optimum values of the parameters, test measurement and recognition processing are repeated while the parameter settings are changed, and it is necessary that the recognition result is confirmed every time, which uses a large amount of user's energy. Moreover, when a load on the user is increased by the work, versatility and user-friendliness of the device are lost.